
\section{Simulation of excitatory postsynaptic currents (EPSCs)}

To account for the dendritic filtering of the synaptic inputs, excitatory postysnaptic currents (EPSCs) were simulated using a detailed passive cable model of a CA3 pyramidal neuron implemented in NEURON 7.3 with Python 2.6 as interpreter. The cell morphology was based on reconstruction of soma and dendrites of a biocytine-labeled rat CA3 pyramidal cell neuron. Specific membrane capacitance (Cm) was 1 $\mu F cm^{-2}$, specific membrane resistance (Rm) 164,000 $\Omega cm^2$ and axial resistance (Ra) 194 $\Omega cm$.

Postsynaptic conductance was computed by the product of two exponentials with time constant of 0.2 ms for rise and 2.5 ms for decay. The reversal potential was assumed to be 0 mV. The synaptic peak conductance was adjusted to 0.3 $\mu S cm^{-2}$.

To evoke synaptic events, 20 presynaptic stimulations were delivered every 50 ms and synaptic events ocurred at a fixed probability of 0.3 during that period.

For simplicity, simulation did not account for inter-site variability (i.e variation of quantal size within contacts) of or intra-site variability (i.e variation in the quantal size among contacts). Release probability was defined as the probability of releasing one \emph{quanta} of conductance within the time interval of 50 ms. No short-term dynamics was assumed during this time interval but only temporal summation of EPSCs. Release probability was assumed to be constant and independent in every synaptic contact. Recording noise (e.g white noise) was not incorporated and low pass filter through the series resistance (0.1 $M\Omega$) of the recording pipette was accounted.

\newpage{}
\subsection{Simulation with a single synaptic contact}
A single synaptic contact located at 171 $\mu m$ from the soma was simulated on a passive CA3 pyramidal neuron. Presynaptic stimulation consisted of a train of 20 pulses delivered at 20 Hz and the release probability was set to 0.3. Simulation presents a larger number of failures in synaptic transmission, and synaptic currents of low magnitude.

\begin{center}
\includegraphics[width=\textwidth]{./figures/1contact.pdf}
\end{center}

\subsection{Simulation of ten synaptic contacts}

Ten synaptic contacts were alocated at distances between 170 and 270 $\mu m$ from the soma. Presynaptic stimulation  was the same as before (20 stimuli at 20 Hz). The release probability of each contant (0.3) was constant and independent. Temporal summation was assumed. Due to the high number of synaptic contacts, no failures in synaptic transmission were observed.
\begin{center}
\includegraphics[width=\textwidth]{./figures/10contacts.pdf}
\end{center}
